The present invention relates to refrigerant compressors, and more particularly to discharge valve assemblies for such compressors.
There are various types of refrigerant compressors which perform the function of compressing refrigerant fluids. These include reciprocating compressors, rotary compressors, and scroll compressors.
Reciprocating compressors include at least one cylinder with a piston reciprocating therein so as to both draw fluid into the cylinder and thereafter compress the fluid before discharge. Such a compressor requires a means for regulating both the inflow and outflow of the fluid to and from the cylinder.
A rotary type refrigerant compressor typically includes a roller or piston, which rotates or orbits within a cylinder in such a manner so as to define a compression chamber and a suction chamber. The rotary piston rotates beyond a top dead center position to a point where the compression chamber is at a maximum volume. As the rotary piston rotates beyond the top dead center position, it begins to compress refrigerant fluid contained in the compression chamber. This compression of the refrigerant fluid continues until just prior to the top dead center position where the compression chamber is now adding minimum volume. It is necessary to provide a means for regulating the inflow and outflow of the fluid to and from the cylinder within the rotary type refrigerant compressor also.
A discharge valve is normally used to regulate the outflow of compressed fluid in both reciprocating and rotary compressors. The discharge valve is in communication with the compressor chamber provided in a cylinder head of the rotary compressor or in a valve plate adjacent the cylinder in a reciprocating type compressor. The discharge valve may be of the flat leaf spring-type in either compressor. Typically in a rotary compressor, the flat leaf spring-type valve is biased toward a valve seat while a volume of fluid is compressed with increasing force within the compression chamber. At a certain point, the force becomes sufficient to overcome the biasing of the leaf spring, thereby causing the valve member to become unseated so as to allow compressed refrigerant fluid to enter a discharge chamber.
A problem with such leaf spring valve members has been that they do not extend into the discharge port. This results in a volume of fluid in the discharge port which re-expands in the cylinder during the next cycle of suction.
Various valve arrangements have been devised which extend into the discharge port so as to thereby reduce the re-expansion volume. An example of such is found in U.S. Pat. No. 5,775,894, which discloses a rotary-type compressor with a discharge valve having a discharge ball which is biased against the discharge port. This particular discharge valve arrangement requires both a discharge ball and a separate discharge valve stem as well as a machined valve seat to accommodate the spherical ball. Another example of a discharge valve device is disclosed in U.S. Pat. No. 4,580,604. This patent discloses a discharge valve having an elliptical curved cross section, which extends into the valve port. This valve assembly also requires a machined valve seat so as to conform to the elliptical shape of the valve.
A problem with the above described discharge valves is that flow separation occurs at some point along the curved portion of the valve when compressed refrigerant flows out of the discharge port. This tends to decrease the overall effective clearance volume between the valve and the valve seat. It moreover produces a certain amount of kinetic energy formed at the point of flow separation, which can produce an unacceptable noise level when the valve opens.
The present invention provides a shaped valve which extends into the discharge port so as to reduce the re-expansion volume. The shaped valve includes a convex portion on the seat side of the valve which extends downwardly into the discharge port. The shaped valve furthermore includes a concave portion on the seat side of the valve that begins where the convex portion ends. The beginning of the concave portion on the seat side of the valve is located so as to prevent flow separation of the refrigerant when flowing along the convex portion of the valve as it leaves the compression chamber of the compressor. The beginning of the concave portion can be defined by a radius measured from the centerline of the discharge port to the circumference of a circle defining where the convex portion ends or the concave portion begins. This radius is greater than one-half of an inside radius as measured from the centerline of the discharge port to the innermost point of contact of the valve seat with the seat side of the valve.